Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

7
Default and
Non-Monotonic
Reasoning
This chapter briefly outlines the scope of automated reasoning in the absence
of complete knowledge about the world. The incompleteness of facts or
knowledge may appear in a reasoning system in different forms. There is no
general notion to treat the different types of incompleteness of data and
knowledge (clauses) by a unified approach. In this chapter, we cover 4
distinct techniques, all of which, however, may not be applicable to a
common problem. The techniques are popularly known as default logic, nonmonotonic
logic, circumscription and auto-epistemic logic. Informally,
default logic infers a consequent, when its pre-conditions are consistent with
the world knowledge. The non-monotonic logic works with two modal
operators and can continue reasoning in the presence of contradictory
evidences. Circumscription is an alternative form of non-monotonic
reasoning, which attempts to minimize the interpretations of some predicates
and thus continues reasoning even in the presence of contradictions. The
auto-epistemic logic that works on the belief of the reasoning system,
occasionally changes inferences, as new evidences refute the existing belief.